This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-192757, filed Jun. 27, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The invention relates to a data-processing apparatus, such as a personal computer, which has a nonvolatile storage device, and to a method of controlling the rewriting of the nonvolatile storage device incorporated in a data-processing apparatus.
2. Description of the Related Art
In recent years, various portable, battery-driven notebook-type personal computers have been developed. Each notebook-type personal computer incorporates an electrically programmable nonvolatile storage device such as a flash memory. The nonvolatile storage device stores a BIOS (Basic Input/Output System). It may be electrically programmed, whereby the BIOS is easily updated to new version.
It is usually necessary to use two items to update the BIOS in a personal computer. The first item is a new-version BIOS image file. The second item is a flexible disk (FD) that stores a BIOS-updating system program. The flexible disk is inserted into the personal computer. The computer is then powered on. The computer is thereby booted up from the flexible disk and starts executing the BIOS-updating system program. The BIOS-updating system program rewrites the nonvolatile storage device in the format of the new-version BIOS image file. Thus, the BIOS is updated to the new version.
Recently, it has been proposed that the BIOS be updated from application software that operates on an operating system (OS). In this BIOS-updating method, it is unnecessary to boot up the system from a flexible disk. Hence, the BIOS can be easily updated, even in so-called xe2x80x9cFDD-less personal computersxe2x80x9d that do not incorporate a flexible disk drive (FDD). The procedure of rewriting the nonvolatile storage device to update the BIOS varies in accordance with the platform of the personal computer. But most of rewriting procedures are disclosed. Hence, any person can easily rewrite a nonvolatile storage device, only if he or she prepares application software that performs the procedure of rewriting the nonvolatile storage device.
A person may prepare, in bad faith, software (i.e., virus) for corrupting BIOS and may distribute it to personal computers through a network such as the Internet. In this case, the BIOS in any personal computer that executes this software will be destroyed.
An object of the present invention is to provide a data-processing apparatus in which a nonvolatile storage device is protected from wrong rewriting of its contents which therefore has a high security level.
Another object of the present invention is to provide a method of controlling the rewriting the nonvolatile storage device incorporated in a data-processing apparatus.
To attain the objects, a data-processing apparatus according to the present invention comprises: a nonvolatile storage device; a controller configured to rewrite the contents of the nonvolatile storage device; means for accessing the controller to rewrite the contents of the nonvolatile storage device; means for determining whether the access made by the accessing means is a right one or not; and means for prohibiting the controller from rewriting the contents of the nonvolatile storage device when the determining means determines that the access made by the accessing means is a not right one.
In the data-processing apparatus, the accessing means may make an access to the controller to rewrite the contents of the nonvolatile storage device. When the accessing means makes such an access, it is determined whether the access is a right one or not. If the access is a not right one, the rewriting of the contents of the nonvolatile storage device is prohibited at once. Hence, the security level of the apparatus can be increased.
Preferably, the data-processing apparatus further comprises a CPU; and an interruption signal generator configured to generate an interruption signal to the CPU when the accessing means accesses the controller. The determining means is activated by the CPU when the CPU receives the interruption signal.
Preferably, the data-processing apparatus further comprises signal-masking prohibiting circuit that prohibits masking of the interruption signal.
To prevent an accidental rewriting of the contents of the nonvolatile storage device, it is desirable that the controller should have a write-protecting function for protecting the contents of the nonvolatile storage device from the accidental rewriting. Then, the interruption signal generator generates the interruption signal when the software releases the write-protecting function of the controller by accessing to the controller. If the access is a wrong one, the write-protecting function is returned active state, thereby to prohibit wrong rewriting of the contents of the nonvolatile storage device.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.